Telescopic riflescopes have been used by hunters for many years. Simple versions of riflescopes include devices whose power settings are fixed at a single power magnification which may be as low as, for example, three power (3X), and may range up to higher magnifications on the order of forty power (40X). However, as stated, the power setting of such riflescopes is fixed and, therefore, cannot be changed.
In certain situations, lower powered riflescopes are desirable as the field of view available to the hunter is extensive. However, as can be readily understood, there are many instances where higher powered riflescopes are desirable for improved aim, and the like. But, increased power is accompanied by a proportionate decrease in the field of view. Also, of significance is the fact that by increasing the power of magnification the amount of illumination transmitted through the optical system is proportionately decreased. This condition contributes to the difficulty of defining a target at higher power magnifications when lighting conditions are minimal, such as occur during early morning and early evening hours.
Inevitably, a riflescope was devised which incorporated a mechanism capable of providing more than one power setting. This was accomplished by interconnecting the lenses contained within the erector lens assembly to a power change ring mounted externally about the riflescope housing adjacent the eyepiece. Rotation of the power change ring caused the lenses of the erector lens assembly to be moved which, in turn, provided a change of magnification of the object being viewed. This achievement provided a significant advantage over the fixed single power riflescopes previously available to hunters. Examples of riflescopes incorporating such mechanism may be seen in U.S. Pat. Nos. 3,213,539; 4,255,013; 4,789,231 and 4,986,645.
However, because of its design, the variable power riflescopes incorporated an inherent disadvantage. Briefly, in many situations in the field, it is normal practice for a hunter to set the power to one of the lower available magnifications, such as three power (3X) or four power 4X), in a typical variable riflescope such as a 3X-9X model. The hunter then scans the terrain in order to determine if there is any game in the area. As the lower power setting provides a much greater and brighter field of view than would a higher power setting, the hunter is readily able to scan large areas of terrain with a relatively quick sweep of the firearm and mounted riflescope. Should a target be defined within the field of view, it then becomes necessary for the hunter to increase the power setting to a higher magnification in order to more clearly define the target within the field of view. This requires manual rotation of the power change ring. It will be appreciated that in transition from low to high power the target image may be lost as the riflescope is swiveled or rocked from the original line of sight. The hunter must then repeat the entire process until the target image is maintained at the desired higher magnification. As game animals are acutely sensitive to movement, they are often spooked by the actions of the hunter in this power setting process and leave the area being scanned thereby frustrating the hunter in his attempt to get off a shot.
In an attempt to overcome the problems referenced above, V. R. Sandall in U.S. Pat. No. 4,952,041 discloses a riflescope which incorporates a battery operated motor connected to a zoom lens assembly by way of gearing to effectively cause the zoom lens assembly to either increase or decrease the power of magnification upon movement of an external mounted switch.
While the riflescope described in this particular patent does provide a solution to the problem inherent in the previously described riflescopes, it does itself suffer from several inherent problems. The first and most significant is that the riflescope depends upon an electronic motor whose energy source is batteries for its automatic zoom mode. It is evident that in order for the riflescope to function properly that both the batteries and the motor must be maintained in good order. Should the batteries lose their electrical charges, the power zoom capabilities of the riflescope are effectively disabled. Also, should the motor become disabled, the power zoom mechanism is, in turn, disabled. Should any of these devices fail while the hunter is in the field, the probability of acquiring game is significantly reduced.
A further problem encountered by this scope is one of noise. As the zoom mechanism is drawn by an electronic motor and gear mechanism, it inherently emits noise when energized. As most game animals have very acute hearing, there is a likelihood that the game may detect noise and be frightened away from the area before the hunter can get off an accurate shot.
A still further problem with a riflescope of this type is on of cost. Although modern electronics are fairly economical in and of themselves, their addition to a sports optics device, such as a riflescope, will surely result in a much more costly product.
In view of the above, there still remains a strong need for a riflescope which features a simple, low-cost non-electric apparatus for automatically and rapidly changing the power settings.